Fairfax Media Network

Agriculture Weather


Southern Oscillation Index

  • location
  • Aus

The Southern Oscillation Index (SOI) is calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin.

A strongly and consistently positive SOI pattern (e.g. consistently above about +6 over a two month period) is related to a high probability of above the long-term average (median) rainfall for many areas of Australia, especially areas of eastern Australia (including northern Tasmania) - La Niņa.

Conversely, a 'deep' and consistently negative SOI pattern (less than about minus 6 over a two month period, with little change over that period) is related to a high probability of below median rainfall for many areas of Australia at certain times of the year - El Niņo.

However, it is important to remember that the pattern of relationship between SOI and rainfall (and temperature) can vary depending on the particular season and region. Additionally, the change in SOI over a specified period can be as important in understanding relationships between SOI and rainfall as is the absolute value in SOI.

Southern Oscillation Index

SOI

Nino3.4 Index

Nino3.4
Display Your Local Weather

Weather News

NSW weather: Severe thunderstorm works its way from Sydney to state's north

22:27 EDT

Trampolines have flown into powerlines and a lightning strike has reportedly caused a house fire as a severe thunderstorm tracked from Sydney all along the coast up to northern NSW on Monday afternoon.

A case of history repeating itself: What is wrong with South Australia's electricity network?

18:43 EDT

Those who blamed last week's blackout in South Australia on renewable energy are dead wrong.

Stormy Monday across Australia

17:03 EDT

Thunderstorms are affecting six states and territories this afternoon, four of which are under warning for severe storms.